>>1
Numerous reasons, and if nothing else, dedication to foreign policy that is outdated.
Initially, support of Israel gave Jews a place to settle after WWII, have another partner in the Middle East, and whatever other paranoid reasons that various shills throw out. After a variety of gaffes on our part based on our dedication to Israel and oil, the entire area went (even more) to shit.
So, we now have a country which can be characterized directly or indirectly by any leader in the area who wants to put blame somewhere else for current conditions. Besides notions of Jewish plots and schemes, it seems the biggest reason to support Israel is the mere fact that we would take a severe blow to world view if we were to outright abandon a staunch ally at this point.
All of this is merely off the cuff notions, there is probably a lot more or a lot less to it. However: would abandoning Israel make the area more stable? would it make Muslim fundamentalists less likely to hate us? would we save money and lives in the long term? what would losing Mossad as an intelligence source do to us?
More informed people than the mighty toughguys of 4chan seem to think a qualified 'No' is the answer to the first three, and wouldn't like to even think of an answer to the last.